Bridge Classes

Dynamic View Services > Implementing a Representation Model > Implementing a Tree Representation Model > Bridge Classes

Bridge Classes

To build a bridge between the generic representation protocol and the graphic classes, we declare two new classes: TreeR which makes up the bridge to TreeGadget and TreeItemR which makes up the bridge to TreeGadgetItem.

To be used as bridge classes, the classes TreeR and TreeItemR must:

derive directly or transitively from the class IlsRpObject;

include specific server declarations made via the macro ILS_RP_OBJECT_DECL.

define a constructor that takes the following parameters:

A reference to the representation (that is, to an instance of the class IlsRepresentation) to which the representation object belongs.

A reference to the dynamic representation object model (that is, to an instance of the class IlsRpObjModel) to which the server refers when acting on this object.

In addition to these general declarations, bridge classes define specific members, namely:

The functions and data used to apply the updates requested by the server. For instance the class TreeR declares a function to set the root label. It also has a single data member with a pointer to the tree gadget, to which it delegates the graphical operations.

The callback functions and, optionally, data in charge of notifying the server about the modifications directly performed by the component on the graphical object. For instance, the class TreeR declares a function onSetLabel that is activated by the graphic gadget through a mechanism of callbacks when the label of the gadget is modified.

Below is the synopsis of the class TreeR:

class TreeR : public IlsRpObject

{

public:

TreeR(IlsRepresentation& rp, const IlsRpObjModel& m)

: IlsRpObject(rp,m), _gadget(0) {}

~TreeR();

// update functions

void setLabel(IlsString label);

// callback functions

void onSetLabel(IlsString label);

void onDelete();

TreeGadget* getGadget(){return _gadget;}

private:

TreeGadget* _gadget;

ILS_RP_OBJECT_DECL(TreeR)

};

Note that TreeR does not maintain the tree structure locally.

Similarly, the class TreeItemR defines its own members. In particular, it defines two functions that attach a new item either to a tree or to another tree item. It also defines the symmetric callback functions and maintains a pointer to the TreeGadgetItem to which it delegates the graphical operation.

Below is the synopsis of the class TreeItemR:

class TreeItemR : public IlsRpObject

{

public:

TreeItemR(IlsRepresentation& rp, const IlsRpObjModel& m)

: IlsRpObject(rp,m), _gadgetItem(0) {}

~TreeItemR();

// update functions

void setLabel(IlsString l);

void setOwner(TreeR*);

void setOwner(TreeItemR*);

// callback functions

void onSetLabel(IlsString l);

void onSetOwner(TreeR*);

void onSetOwner(TreeItemR*);

void onDelete();

TreeGadgetItem* getGadgetItem();

private:

TreeGadgetItem* _gadgetItem;

ILS_RP_OBJECT_DECL(TreeItemR)

};

Version 6.3